1. Field of the Invention
The present invention has as object a range of exhaust silencers or mufflers for internal combustion engines, which can be used particularly on vehicles such as motor cars and motor cycles.
A large number of silencers are already known for internal combustion engines. They generally comprise an external case forming a closed enclosure, pierced with at least two orifices for the inlet and outlet of exhaust gases respectively and adapted for connection to an inlet tube and an outlet tube conducting the gases. The closed case contains means for expanding the exhaust gases and conducting them between the inlet and outlet orifices.
2. Description of the Prior Art
The most widely used case structure, described for example in the document U.S. Pat. No. 3 337 939, comprises a tubular peripheral sidewall developed lengthwise along a longitudinal axis, said peripheral sidewall being connected at its ends to two transverse end walls by peripheral crimping forming a bead. Such a structure has the drawback of relatively short life, due particularly to the presence of the peripheral connecting crimping between the sidewall and the end walls, which crimping is formed in a zone forming a wedge in which chemical reactions take place which progressively attack the metal forming the cases. Furthermore, the external profile of such a silencer, having peripheral beads, leads to an increase of the overall diameter of the silencer, for a given inner volume, and the result is a reduction of the useful volume with respect to the total external volume and a reduction of efficiency. Also, this silencer structure is not adapted to the production of a range of silencers of different sizes: to produce two silencers of different lengths, it is necessary to provide longitudinal tubular peripheral cases of different lengths.
Another silencer structure is described in the document FR-A-2 467 974. In this document, the silencer is formed of an external protecting case comprising two semi-cylindrical half shells connected together along two flattened end generatrices, the corresponding generatrices being assembled together by crimping and thus forming two diametrically opposite beads occupying the whole length of the silencer. The external lateral beads increase the size of the silencer, for an equal internal volume. Furthermore, to produce a range of silencers of different lengths, it is necessary to provide half shells having the total length of each silencer. This structure is therefore not adapted to the construction of a range of silencers of different lengths.
The object of the present invention is to avoid the drawbacks of such traditional silencer structures, by providing a new structure which, from a limited number of standard elements, makes it possible to produce silencers whose lengths are different. For that, a more or less large number of different unitary elements are fitted axially end to end to produce silencers whose diameters are substantially identical but whose lengths depend on the number and structure of the assembled elements.
Silencer structures are already known formed by axially assembling end to end at least two unitary elements, each unitary element being formed of an axial peripheral sidewall defined at its upper end by a free annular edge and connected at its second end to a radial portion forming a silencer transverse end wall. Such structures are described particularly in the documents U.S. Pat. No. 2 205 024, DE-C-402 357, DE-A-2 623 153, U.S. Pat. No. 3 670 845.
It proves that a structure such as described in the document U.S. Pat. No. 2 205 024 is difficult to produce for the two free edges of the two parts to be assembled together are guided by no guide means during assembly thereof. The result is welding defects and a great manufacturing complexity.
The documents DE-C-402 357, DE-A-2 623 153 and U.S. Pat. No. 3 670 845 teach an assembly using an external sleeve covering externally the two edges of the elements to be assembled together. This structure is not adapted to assembly by welding, it increases the external size of the silencer and complicates manufacture, without giving satisfactory results from the point of view of sealing and mechanical strength of the assembly.